Things that need to be cleaned up in quota-tracking.html:
-- Remove all trailing whitespaces
-- Refactor errorFunction(). Right now, it takes two parameters (tx, error) and is used as the error function for both executeSql() and transaction(). The problem is that transaction()'s error callback uses only one parameter. So if a transaction fails, the error gets assigned to the 'tx' parameter, and the 'error' parameter is left undefined; this leads to an exception when errorFunction() tries to log 'error.message'.